Exhaust silencer for internal combustion engines



H. C. AUSTIN Feb. 18, 1936.

EXHAUST SILENCER FOR INTERNAL COMBUSTION ENGINES Filed March 17, 1933INVENTOR Harry 6. flush/7 44.42

ATTORNE Patented Feb. 18, 1936 EXHAUST SILENCER FOR INTERNAL COMBUSTIONENGINES Harry 0. Austin, Kansas City, Mo., assignor to Chester L.Austin, Kansas City, Mo.

Application March 17, 1933, Serial No. 661,314

2 Claims. (Cl. 137160) My invention relates to exhaust silencers forinternal combustion engines and more particularly to a device adapted toeliminate the concussion from the exhaust of large Diesel engines.

The exhaust of large internal combustion engines of the Diesel typecreates considerable noise. The use of Diesel engines to furnish powerfor industrial plants has necessitated the building of large mufflerpits. The principle of all mufflers hitherto developed has been to slowdown the exhaust gases to velocities below that of sound. The volume ofthe gases is generally from six to eight times that of the pistondisplacement which in the case of large Diesel engines is considerable.The building of concrete mufiie pits involved considerable expense,inasmuch as the volume of the pit must be usually about twenty times thetotal piston displacement. Frequently, in the starting of engines,ignition does not take place immediately, with the result that the pitbecomes filled with unburnt gases and air. This mixture is usually anexplosive mixture with the result that, when ignition does take placeand explosion follows, it frequently is of considerable violenceresulting in injury to limb and property.

In two-cycle Diesel engines, it is essential for efliciency that theback pressure be not increased. Types of mufflers which depend uponbaflling and giving the exhaust gases a circuitous path through bailiesand apertures tend to increase the back pressure. A frequent source ofdifiiculty is the clogging of the apertures by carbon depositions andresinous material which render the mufiier inoperative after a period ofuse. These devices, too, are of considerable size and unless extremelystrongly built, it is found that the bafiles will vibrate and makeconsiderable noise.

One object of my invention is to provide a strongly constructed, simplesilencer for the exhaust of internal combustion engines.

Another object of my invention is to provide a silence-r which will notincrease the back pressure materially.

Another object of my invention is to build a muffler which is light andsmall in size so that it may be installed directly in the exhaust pipefrom the engine at any convenient part thereof.

Still another object of my invention is to provide a construction inwhich the danger of damage due to explosions of unburnt fuel iseliminated.

In the accompanying drawing which forms part of the instantspecification and is to be read in conjunction therewith and in whichlike reference numerals are used to indicate like parts in the variousviews;

Figure 1 is an elevation, of my device installed in the exhaust pipe ofa large Diesel engine.

Figure 2 is a sectional view of my silencer with the outer casing insection.

Figure 3 is a sectional View of my muffler with the outer and innercasings in section.

Figure 4 is a plan view taken on the line 44 of Figure 3.

In general, my invention contemplates providing a plurality of paths forthe exhaust gases. Each path is of different length so that interferencebetween the sound waves will be caused. The paths are adapted to givethe exhaust gases a whirling motion and are substantially unobstructedto obviate the danger of clogging or of explosions. Likewise,unobstructed paths, I have found, will prevent the building up of backpressure. A pair of muffler sections are mounted in series separated byan adjustable tuning chamber. Frequently the principle of resonanceamplifies the sound which remains after the gases pass through a mufliersection. By adjusting the tuning chamber to the point of greatestdissonance, the sound is effectively muted with the result that theexhaust will be inaudible at the exit of the exhaust pipe.

More particularly referring now to the drawing, an exhaust pipe I leadsthe exhaust gases from the exhaust manifold of the internal combustionengine. Secured to the exhaust pipe I in any suitable manner, such as bya bolted flange 2, is a first section 3 of my muffler. This sectioncomprises an outer casing 4 provided with a bolting flange 5. Within thecasing 4 and in spaced relation thereto I provide a second casing 8.Between casings 4 and 8, I position a pair of helical baffles 6 and lwhich are welded to the inner surface of casing 4 and the outer surfaceof easing 8. It is to be understood, of course, that, while I have showna pair of helical baffles, a single helical baflle or a plurality ofhelical bailies of any suitable number may be employed. The object inusing more than a single helical bafile is to provide a spiral path oflesser pitch than would be required for a single helical baffle. Thereduction of the pitch renders the component of back pressure created bythe resistance of the baflies smaller than would be the case if a singlebaffle were used. Casings 4 and 8 are mounted in concentric relation.While I prefer to use cylindrical casings, it is to be understood thatcasings of any suitable cross sectional shape may be employed. Iposition a tube 9 with its axis coincident with the axes of casings 4and 8. Between tube 9 and casing 8 I provide a second pair of helicalbaflles Ill and I I. These baflles are welded to the exterior of tube 9and to the interior of casing 8 and form an unobstructed path for theexhaust gases. It is to be noted. that the gases passing through thepassage l2 which is formed by casings 4 and 8 will have a. much longerpath of travel than the gases passing through the passage I4. A certainportion of the exhaust gases may pass directly through the tube 9 and,this being a straight path, will be the shortest path. Casing 4 has askirted projection l5 extending beyond the baflle section. I provide acylindrical member l6 adapted to telescope with skirt l5, as can bereadily seen by reference to Figures 2 and 3. Member [6 is provided witha flange l1 and a flange I8. Flange I8 is adapted to be bolted to flange5 of muilier section 3' which is identical to the mufller sectiondescribed above. The reference numerals applied to mufiler section 3'will be the same as those applied above, with primes to distinguish thatthey refer to the second muffler section. Around the exterior of casing4 I weld a flange l9. Flange I9 is supported by triangular bracingmembers 20, welded thereto as can be readily seen by reference toFigure 1. Flange I1 is likewise provided with bracing members 2|.Secured to flange I9 are bolts 22 which are provided with adjusting nuts23 and 24 as can be readily seen by reference to Figures 2 and 3. Itwill be readily appreciated that, by the respective loosening of nuts 24and the tightening of nuts 23 that the casing IE will be moved to agreater depth of telescoping with skirt portion l5. This will result ina decrease of the size of the chamber 25, which as pointed out above, isthe tuning chamber. By adjusting the chamber volume by the adjustmentjust described, a position of greatest dissonance may be reached,resulting in effective silencing. Very frequently a single mufflersection and a tuning section are all that is required for silencing toan extent sufiiciently great to render the exhaust innocuous as far asthe nuisance eifect of the exhaust noise is concerned. In zones whereextreme silence is required, as for example in the vicinity of a thicklypopulated district, a second mui'lier section 3 may be installedoutwardly of the first mufiler section. If desired, a plurality ofmuliier sections as needed may be required, though I have found that inno event is it necessary for practical purposes to use more than twomuffler sections. In event that only one muffler section is employed,casing I5 may be the terminal portion of the exhaust pipe. In event thetwo muffler sections are employed as shown in Figure 1,'a

length of eduction casing 26 may be bolted to the second muillersection.

In practice, I have installed a muffler made according to my inventionon a commercial unit in which the exhaust of a Diesel engine having fivecylinders 16 inches in diameter and employing a stroke of 20 inches wasto be silenced. The engine exhaust pipe was 24 inches in diameter. Theexternal diameter of my muiiier was no greater than the diameter of theexhaust pipe, that is 24 inches. The entire length of my muflier wasonly 6 feet. The exhaust was eifectively silenced so that it wassubstantially inaudible within a radius of 10 feet. No vibration wasperceptible. The

engine on which my mufiler was installed, had been employing a.commercial type of muiiler. It measured 23 feet in length and 42 inchesin diameter. The exhaust was not effectively silenced and the vibrationoccasioned by the muffler baffles made considerable noise in and ofitself.

It will be obvious that I have accomplished the objects of my invention.Due to the fact there are no small openings for the dispersion of theexhaust gases, the danger of clogging, due to carbon deposition isobviated. Due to the fact that the passage for the exhaust gases issubstantially unobstructed, not only is loss of efficiency dueto backpressure prevented but the danger of explosion damage is obviated. Itwill be clear from the above description that in event unburnt gases doignite, they will blow harmlessly out of the muffler pipe without doingdamage. My muffler is of rigid construction and light in weight. Thereare no loose parts to vibrate and it may be conveniently installed atany desirable point. I have found that it is advisable in practice toinstall it near the terminal end of the exhaust stack.

It will be observed that, by creating three paths for the exhaust gases,of different length, that the exhaust gases will arrive at the outlet ofthe muffler section at diiferent times causing an interference of thesound waves tending to reduce their intensity. Likewise, the impartingof a whirling motion to the gases will not only tend to cut down theirforward velocity but will cause turbulence which will result in thedestruction of the sound waves. It is to be noted that the spiral pathin passage I2 is opposite in direction of rotation from the spiral path[4. If desired, the spiral paths l2 and I4 may be given the samedirection.

It will be understood that certain features and sub-combinations are ofutility and may be employed without reference to other features andsub-combinations. This is contemplated by and is within the scope of myclaims. It is further obvious that various changes may be made indetails within the scope of my claims without departing from the spiritof my invention. It is, therefore, to be understood that my invention isnot to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. An exhaust silencer comprising in combination a helical bafiiestructure providing a plurality of paths of different length, anenlarged chamber communicating directly with said baffle structure,means to vary the volume of said chamber to a predetermined point and asecond baffle structure directly communicating with said chamber.

2. An exhaust silencer comprising in combination three imperforatecasings having different cross sectional areas and disposedconcentrically in spaced relation to each other and forming threepassageways, said passageways having direct communication with theexhaust to be silenced whereby three paths are provided for the eductionof the exhaust gases, means constraining the exhaust gases to flowthrough the outer two passageways in respective helical paths ofdifferent length, the central casing being unobstructed and providing adirect path of flow for a portion of said gases.

- HARRY C. AUSTIN.

